The invention concerns a device for processing workpieces using ultrasound, comprising an ultrasound sonotrode and an anvil, wherein a workpiece is processed between the ultrasound sonotrode and the anvil.
Ultrasound processing devices of this type join or connect workpieces. Such devices also weld or separate, i.e. cut, workpieces. These devices may also be used to fix a first workpiece part to a second workpiece part at a certain position. In such processing workpieces, certain workpiece areas must often be protected from the ultrasound. Certain individual components which must not be welded to each other, must e.g. be fixed, held or damped. Moreover, the components should also be reliably fixed prior to processing.
Flexible mold parts are conventionally used, which are glued into or clamped to the sonotrode front ends to damp certain component areas during processing. Such damping elements, however, do not permit precise fixing. The service life of these elements is also relatively short and matching of the pressure is highly problematic due to the high spring constant or the short spring length of such damping elements.
In addition to prior art in accordance with DE-A-25 08 175, DE-A-10 68 646 and GB-A-1 262 534, DE-U 92 12 560 discloses spring-supported, leading holding-down devices which are supported and guided outside of the sonotrode. They may be pressed onto the workpiece to be processed outside of the sonotrode, or the holding-down devices are guided to the inside of the sonotrode as is disclosed in DE-U-87 02 983. The disadvantage of such designs is that the structure is relatively complex and requires a substantially large amount of space. Moreover, these systems are also pretensioned by mechanical springs. The pressure is therefore not constant and depends on the path.
In other embodiments, the holding-down device, which is pretensioned by a spring, is disposed in the oscillation node of the ultrasound sonotrode. These devices are problematic in that oscillations are still transmitted and exact bearing at the oscillation node is only theoretically possible, since the entire screwed joint or mounting of such a holding-down system extends over a larger area, beyond the oscillation node. This results in heating, vibrations and an increase in power loss of the overall system, which reduces the service life and limits the reliability of such systems.
It is therefore the underlying purpose of the invention to further develop a device of the above-mentioned type in such a fashion that the ultrasound sonotrode can be provided with a holding-down device or a damping element of simple and compact construction.